Headless Compression Screw Fixation for Proximal Phalanx Fractures: A Biomechanical Study

Area of Science:

• Orthopedic surgery
• Biomechanics
• Hand surgery

Background:

• Proximal phalanx fractures are common hand injuries.
• Intramedullary (IM) screw fixation is an emerging treatment with promising early results.
• Limited biomechanical data exists for IM screw fixation of these fractures.

Purpose of the Study:

• To biomechanically compare two methods of IM screw fixation for proximal phalanx fractures.
• To evaluate the effect of a blocking screw on construct stability.
• To assess the influence of specimen size and screw fill on fixation stiffness.

Main Methods:

• Cadaver proximal phalanges underwent IM screw fixation.
• Two groups: single antegrade headless compression screw vs. screw plus blocking screw.
• Apex volar 3-point bending tests were performed using a Materials Testing System.

Main Results:

• No significant difference in stiffness between single screw and screw with blocking screw fixation (P = .27).
• Smaller specimens demonstrated significantly greater stiffness than larger specimens (P < .0002).
• A moderate positive correlation between screw fill percentage and stiffness was observed (r = 0.51).

Conclusions:

• A blocking screw does not enhance the stability of IM screw fixation for proximal phalanx fractures.
• Smaller bone size and a higher screw length to bone length ratio are associated with increased stiffness.
• Findings offer valuable insights for evolving IM screw fixation techniques in hand surgery.